New research: Language gap in children starts at 18 months

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New research indicates that the language gap between children of low socio-economic groups and their more well-to-do peers may begin as young as 18 months old.

Published in Developmental Science, Stanford researchers have found that toddlers from low-income households are already several months behind in language acquisition than toddlers from higher income households.

It builds on the famous Hart and Risley studies, which found that children in higher income homes know more words than their lower-income peers - and that gap rarely closes. Children in higher income families have heard up to 30 million more words by age 3. Now, the Stanford research indicates that gap begins at 18 months old.

Stanford professor Anne Fernald and her team studied 20 toddlers of families close to Stanford campus. They assessed the speed and accuracy with which the toddlers identified objects from spoken cues at 18 months and again at 24 months.

The researchers then recruited and tested 28 children in a community in Northern California where the median household income and educational levels were much lower than the sample group.

In the tests, Fernald’s team showed each child an image, followed by a verbal instruction. In one example, the child saw a ball and a dog. The child was then told to “look at the ball” and a video camera recorded the toddler’s eye and head movements. The video was later analyzed by trained “coders” to notice the exact moment when the child’s gaze shifted to the object.

The team measured response time in milliseconds. The toddlers from lower-income and less-educated families were, on average, 200 milliseconds slower to respond than the sample group at 18 months old.

"A 200-millisecond difference in response time at 18 months may not sound like much, but it's huge in terms of mental processing speed," Fernald told the Stanford News.

All the children were faster at 24 months. However, it took the low-income children that long to catch up to where the higher income toddlers were at 18-months-old - meaning they were already six months behind at two years of age.